Custom Proxy

Has anyone created a custom proxy before? For example, let's say that in the portal example from sencha, that you want to add a list of icons to the west panel. From this list of icons, you could drag them onto the central panel, and drop them in to add brand new "portlets". The icon would move the "portlets" around just as though they were part of the original group of "portlets".

My problem is that when I create a list of icons, I get an icon proxy that doesn't do anything to move the "portlets" around. I suppose what I need is actually a panel proxy to achieve this.